Photosemiconductor and optical fiber welded module

ABSTRACT

A photosemiconductor module such as a laser diode module or a photodiode module is optically coupled to an optical fiber. The photosemiconductor module includes a holder assembly with a photosemiconductor and a lens being fixedly mounted therein coaxially along an optical axis. An optical connector is joined to the holder assembly and has a hollow receptacle to be connected to the optical fiber and a joint press-fitted in the receptacle and joined coaxially to the holder assembly by lap laser beam welding.

This application is a continuation-in-part application of U.S. patentapplication Ser. No. 07/647,035, Jan. 29, 1991 now U.S. Pat. No.5,119,462.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a photosemiconductor module capable ofemitting light or detecting the intensity of received light, for use inoptical communications.

2. Description of the Prior Art

Photosemiconductor modules are used to obtain a predetermined coupledcondition between a photosemiconductor and an optical fiber forachieving a desired intensity of light transmitted between thephotosemiconductor and the optical fiber. Generally, thephotosemiconductor modules include a lens to be disposed between thephotosemiconductor and the optical fiber to adjust the coupledcondition.

One conventional photosemiconductor module is shown in FIG. 6 of theaccompanying drawings. The photosemiconductor module includes aphotosemiconductor 100 and a lens 101 which are fixed in position by anadhesive or the like in an integral holder 102 made of brass or thelike. The holder 102 is joined by a solder 104 or laser welding to anoptical connector 103 which includes a receptacle of brass or the likethat is to be connected to a plug (not shown) coupled to an opticalfiber.

Another known photosemiconductor module includes separate holders for aphotosemiconductor and a lens, as disclosed in Japanese Laid-OpenUtility Model Publication No. 63(1988)-128748, for example.

The photosemiconductor modules are however incapable of adjusting thelens along an optical axis thereof (i.e., in the direction of theZ-axis). Therefore, elaborate and detailed design configurations arenecessary to fix the photosemiconductor and the lens to the holder orholders since the photosemiconductor and the lens cannot be relativelyadjusted in position along the optical axis while the optically coupledcondition is being monitored when these photosemiconductors areassembled.

The optical connector 103 shown in FIG. 6 is of a unitary structure. Inorder to join the holder 102 and the optical connector 103 to each otherby the solder 104 or laser beam welding, the optical connector 103 hasto be machined highly accurately from a mass of hard metal which is noteasy to cut.

The holder 102 and the optical connector 103 are held in abutmentagainst each other. When the holder 102 and the optical connector 103are welded to each other by a laser beam, it is required to slightlyadjust the position where the laser beam is applied radially to thejoint between the holder 102 and the optical connector 103, because thearea in which the holder 102 and the optical connector 103 are weldedtogether tends to vary depending on the position where the laser beam isapplied. Consequently, the photosemiconductor modules cannot beassembled efficiently at a high production rate. The qualities, such asmechanical strength and distortion, of the photosemiconductor modulereflect the condition in which the laser beam is applied.

The region where the holder 102 and the optical connector 103 is joinedtogether is exposed to the exterior. Therefore, the joined region haspoor environmental resistance against heat cycles, humidity, and otherenvironmental factors. If the photosemiconductor and the lens are heldin different holders, respectively, relative positional adjustments ofthe holders in directions normal to the optical axis (i.e., thedirections of the x- and y-axes) result in irregularities in the outerprofile of the photosemiconductor module. The outer profile of thephotosemiconductor module is thus liable to have a poor coaxialconfiguration.

In the cases where the components of the photosemiconductor areassembled and secured together by adhesive bonding or soldering, theoptical axis of the module will be slightly deflected in a heat-cycleload test or the like. Then, the photosemiconductor module cannotproduce a stable optical output if the plug is connected to asingle-mode fiber rather than a multimode fiber, and hence is notreliable enough in operation. The adhesive bonding process allows thecomponents to be positionally displaced when the adhesive is heated andhardened, and also requires a certain period of time to elapse until thecomponents are completely joined together. Accordingly, the assemblingprocedure is composed of an increased number of steps and istime-consuming. In addition, although the photosemiconductor module isrelatively simple in construction, it cannot automatically be assembledbecause of the adhesive bonding process required.

SUMMARY OF THE INVENTION

In view of the aforesaid difficulties of the conventionalphotosemiconductor modules, it is an object of the present invention toprovide a photosemiconductor module which is of high quality andreliability, can efficiently be manufactured because of a laser beamwelding process employed, and is of such a structure which can easily beassembled automatically.

Another object of the present invention is to provide aphotosemiconductor module which includes components that canpositionally be adjusted in the directions of X-and Y-axes normal to theoptical axis thereof and also in the direction of the optical axis,i.e., in the direction of a Z-axis.

According to the present invention, there is provided aphotosemiconductor module for being optically coupled to an opticalfiber, comprising a holder assembly, a photosemiconductor and a lenswhich are fixedly mounted in the holder assembly coaxially along anoptical axis, and an optical connector joined to the holder assembly,the optical connector having a hollow receptacle adapted to be connectedto the optical fiber and a joint press-fitted in the receptacle andjoined coaxially to the holder assembly by lap laser beam welding.

The holder assembly may comprise a flange which is joined to the jointby a lap laser beam welding after the flange and the joint arepositionally adjusted in a direction normal to the optical axis, a firsthollow holder having a hollow portion in which the lens is coaxiallyfixedly mounted, and a second hollow holder in which thephotosemiconductor is fixedly mounted, the first and second hollowholders being brought into interfitting engagement with each other afterthe first and second hollow holders are positionally adjusted along theoptical axis.

Alternatively, the holder assembly may comprise a hollow holder in whichthe photosemiconductor and the lens are fixedly mounted coaxially, and acoupling in which the hollow holder is fitted, the coupling and thejoint being joined to each other by laser beam welding.

The above and further objects, details and advantages of the presentinvention will become apparent from the following detailed descriptionof preferred embodiments thereof, when read in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an axial cross-sectional view of a photosemiconductor moduleaccording to a first embodiment of the present invention;

FIG. 2 is an axial cross-sectional view of a photosemiconductor holderand a lens holder of the photosemiconductor according to the firstembodiment;

FIG. 3 is an axial cross-sectional view of a joint and a receptacle ofthe photosemiconductor module according to the first embodiment;

FIG. 4 is an axial cross-sectional view of a modification of thephotosemiconductor module according to the first embodiment;

FIG. 5 is an axial cross-sectional view of a photosemiconductor moduleaccording to a second embodiment of the present invention;

FIG. 6 is an axial cross-sectional view of a conventionalphotosemiconductor module;

FIG. 7 is an axial cross-sectional view of a photosemiconductor moduleaccording to a third embodiment of the present invention;

FIG. 8 is a front view of the flange portion of the photosemiconductormodule of FIG. 7;

FIG. 9 is an outside view of the photosemiconductor module of FIG. 7having a modified sleeve; and

FIG. 10 is a front view of the flange formed as part of the sleeve shownin FIG. 9.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows in cross section a photosemiconductor module according to afirst embodiment of the present invention. The photosemiconductor moduleaccording to the first embodiment includes a light-emitting element suchas a laser diode or the like.

As shown in FIG. 1, the photosemiconductor module comprises aphotosemiconductor 1 fixedly supported in a photosemiconductor holder 3and a lens 2 fixedly supported in a lens holder 4. The lens holder 4 isfitted in the photosemiconductor holder 3, and joined to thephotosemiconductor holder 3 at regions 10 by a laser beam weldingprocess effected from the side of the holder 3. The photosemiconductormodule also has an optical connector 5 which includes a receptacle 6defining a ferrule hole 7 therein. The lens holder 4 has a flange 4F(FIG. 2) held against or superposed on a joint 8 which is partlypress-fitted in the ferrule hole 7. The flange 4F is joined to the joint8 at regions 10 by a laser beam welding process effected from the sideof the lens holder 4. The photosemiconductor holder 3, the lens holder4, the joint 8, and a portion of the receptacle 6 are fitted in andcovered with a sleeve 9. A filler 11 which may comprise an adhesive isdisposed between the sleeve 9, the photosemiconductor holder 3, and thelens holder 4.

The photosemiconductor module of the above-construction is assembled asfollows:

FIG. 2 shows the photosemiconductor holder 3 with the photosemiconductor1 fixedly mounted therein and the lens holder 4 with the lens 2 fixedlymounted therein before the photosemiconductor holder 3 and the lensholder 4 are interfitted. As illustrated in FIG. 2, thephotosemiconductor holder 3 comprises a hollow tubular member having athicker tubular portion 3A and a thinner tubular portion 3B. Thephotosemiconductor 1 is positioned in the thicker tubular portion 3A.The lens holder 4 also comprises a hollow tubular member having atubular portion 4A to be fitted in the photosemiconductor holder 3 andthe flange 4F to be joined to the joint 8 by laser welding. The lens 2is positioned in the tubular portion 4A.

The lens holder 4 is fitted into the photosemiconductor holder 3 and ispositionally adjusted along the optical axis, i.e., in the direction ofthe Z-axis, while their coupled condition is being monitored. Then, thethinner tubular portion 3B of the photosemiconductor holder 3 and thetubular portion 4A of the lens holder 4 are joined to each other at theregions 10 by a laser beam welding process which is effected radiallyinwardly from the side of the thinner tubular portion 3B.

FIG. 3 shows the receptacle 6 and the joint 8 before the joint 8 ispress-fitted into the receptacle 6. Generally, the receptacle 6 iscomplex in shape, and the ferrule hole 7 is required to be finished sothat the diameter thereof is defined highly accurately. Therefore, thereceptacle 6 is made of a material such as brass which can easily bemachined with high precision. The joint 8 is made of a material such asstainless steel which can easily be joined by laser welding. The joint 8and the receptacle 6 as they are press-interfitted make up the opticalconnector 5.

The flange 4F of the lens holder 4 to which the photosemiconductorholder 3 is joined is than held against and superposed on the joint 8,as shown in FIG. 1. While the coupled condition of the lens holder 4 andthe joint 8, i.e., the intensity of light that is transmitted from thelens 2 to the joint 8, is being monitored, the lens holder 4 and thejoint 8 are positionally adjusted in directions of X- and Y-axes normalto the optical axis. Then, the flange 4F and the joint 8 as they aresuperposed one on the other are joined to each other at the regions 10by a lap laser beam welding process which is effected axially from theside of the lens holder 4 to the side of the joint 8.

In this manner, the components of the photosemiconductor module arepositionally adjusted along the optical axis, i.e., in the direction ofthe Z-axis and also in the directions of the X- and Y-axes normal to theoptical axis.

After the coupled condition is adjusted in the directions of the X-, Y-,and Z-axes and the components are joined together, the sleeve 9 isfitted over the joined components, and the filler 11 is introducedbetween the sleeve 9 and the holders 3, 4. The assembling of thephotosemiconductor module is now completed.

The optical connector 5 may be dispensed with, and the optical fiber maybe connected directly to the lens holder 4.

With the above first embodiment, the photosemiconductor holder 3 and thelens holder 4 are separate from each other, and held in interfittedengagement with each other. Therefore, when they are assembled together,they can be positionally adjusted relatively to each other easily andfreely along the optical axis while their coupled condition are beingmonitored.

Since the optical connector 5 is constructed of the joint 8 and thereceptacle 6, they can be joined by laser beam welding and easilymachined with high accuracy since they are made of respective suitablematerials.

The flange 4F of the lens holder 4 and the joint 8 as they aresuperposed are joined to each other by lap laser beam welding.Therefore, the area where the flange 4F and the joint 8 are welded toeach other is not adversely affected by different positions in the laserbeam may be applied. Consequently, the photosemiconductor module thusproduced is of high quality.

The outermost sleeve 9 surrounding the components of thephotosemiconductor module conceal the joined regions and protect themfor increased environmental resistance. The outer profile of thephotosemiconductor module is neat and stable, and can easily be variedinto any of various configurations.

In addition, since the components are joined together by laser beamwelding, the photosemiconductor module can easily be assembled accordingto an automatic process.

FIG. 4 shows a modification of the photosemiconductor module accordingto the first embodiment of the present invention. The modifiedphotosemiconductor module shown in FIG. 4 has an axially split sleeve 15mounted in the ferrule hole 7, with a joint 8, partly fitted in theaxially split sleeve 15. The other structural details are the same asthose of the photosemiconductor module according to the firstembodiment.

A photosemiconductor module according to a second embodiment of thepresent invention will be described below with reference to FIG. 5. Thephotosemiconductor module according to the second embodiment includes alight-detecting element such as a photodiode or the like.

As shown in FIG. 5, the photosemiconductor module comprises aphotosemiconductor 10 and a lens 20 which are fixedly mounted in aholder 30 by solder masses 12. The holder 30 is partly press-fitted in acoupling 13 which is held against and superposed on a joint 30 which ispartly press-fitted in a ferrule hole 7 defined in a receptacle 6. Thecoupling 13 is joined to the joint 30 at regions 10, by lap laser beamwelding.

The photosemiconductor 10, the holder 30, the coupling 13, the joint 30,and a portion of the receptacle 6 are fitted in and covered with asleeve 90 which serves as an outer casing. An adhesive filler 11 isfilled between the sleeve 90, the holder 30, and the coupling 13.

The photosemiconductor module according to the second embodiment isassembled as follows:

First, the photosemiconductor 10 and the lens 20 with its outercircumferential surface plated with gold are disposed in and fixed tothe holder 30 by solder masses 12, thus providing a unitary body. Thephotosemiconductor 10 in the form of a photodiode has a relatively largelight-detecting surface area, and light which is emitted from theoptical fiber plug (not shown) connected to the receptacle 6 passesthrough the lens 20 and is well focused on the light-detecting surfaceof the photodiode 10. For this reason, the photodiode 10 and the lens 20are not positionally adjusted relatively to each other along the opticalaxis, i.e., in the direction of the Z-axis.

Then, the holder 30 with the photodiode 10 and the lens 20 fixedlymounted therein is press-fitted into the coupling 13, which is made of ametallic material such as special stainless steel that can be joined bylaser beam welding. As shown in FIG. 5, the coupling 13 comprises ahollow tubular member including a tubular portion 13A in which theholder 30 is press-fitted and a flange 13F to be joined to the joint 80by laser beam welding.

The joint 80 is press-fitted into the ferrule hole 7 in the receptacle6. As described above in connection with the first embodiment, thereceptacle 6 is complex in shape, and the ferrule hole 7 is required tobe finished so that the diameter thereof is defined highly accurately.Therefore, the receptacle 6 is made of a material such as brass whichcan easily be machined with high precision. The joint 80 to be joined tothe coupling 13 by laser beam welding is made of the same material asthe coupling 13.

The flange 13F of the coupling 13 is then pressed against and superposedon the joint 80. While the coupled condition of the coupling 13 and thejoint 80, i.e., the intensity of light that is transmitted from thejoint 80 to the lens 20, is being monitored, the coupling 13 and thejoint 80 are positionally adjusted in directions of X- and Y-axes normalto the optical axis. Then, the flange 13F of the coupling 13 and thejoint 80 as they are superposed one on the other are joined to eachother at the regions 10' by a lap laser beam welding process which iseffected axially from the side of the flange 13F to the side of thejoint 80.

After the flange 13F and the joint 80 are joined by laser beam welding,the sleeve 90 is fitted over the joined components, and the filler 11 isintroduced between the sleeve 90, the holder 30, and the coupling 13.The photosemiconductor module according to the second embodiment is nowfully assembled.

With the second embodiment, the components are assembled and securedtogether by soldering, press-fitting, and laser beam welding.Accordingly, the components are firmly joined together, and highlyresistant to structural thermal strain under heat-cycle test, and thephotosemiconductor module is highly reliable in operation.

Since the components are put together relatively easily be soldering,press-fitting, and laser beam welding, it is easy to assemble thephotosemiconductor module automatically.

The joint 80 which can be joined by laser beam welding is press-fittedinto the receptacle 6. The receptacle 6 can be made of a material thatcan easily be machined with high precision.

In the second embodiment, the receptacle 6 may be dispensed with, andthe optical fiber may be connected directly to the holder 30.Furthermore, an axially split sleeve as shown in FIG. 4 may be insertedin the ferrule hole 7.

FIG. 7 shows an axial cross-sectional view of a photosemiconductormodule according to a third embodiment of the present invention. Thisthird embodiment of the photosemiconductor module is substantiallysimilar to the structure shown in FIG. 1, but includes a sleeve 309. Thesleeve 309 itself includes a hollow portion 309H as well a diametricallyexpanded flange portion 309F at an end of the hollow portion 309H.

The hollow portion 309H is configured to fit partially over an outer endsurface of an optical connector 305. The optical connector 305 includesa receptacle 306 and a joint 308 fitted into the receptacle 306. As theresult of that configuration, the sleeve 309 surrounding the componentsof the photosemiconductor module serves to conceal the joined regions. Aplastic adhesive 311 is filled through through-holes 300a between thesleeve 309, the photosemiconductor holder 303 and the lens holder 304.The lens holder 304 is fitted into and joined to the photosemiconductor303 by laser beam welding 310. The lens holder 304 is joined to thejoint 308 also by laser beam welding 310.

The flange portion 309F of the sleeve 309 is formed, as shown in FIG. 8,into a substantially oblong shape. The flange 309F of the sleeve 309 isused as a coupling for coupling a connector assembly (not shown) whichcarries an end of the optical fiber and is detachably connected to areceptacle 306 by bolts passing through the through holes 300b in thesleeve 309.

FIG. 9 is an outside view of the semiconductor module of FIG. 7 having amodified sleeve 409. As shown in FIG. 9, the sleeve 409 includes asquare-shaped flange portion 409F.

FIG. 10 shows a front view of the flange portion 409F of the modifiedsleeve 409.

Although there have been described what are at present considered to bethe preferred embodiments of the present invention, it will beunderstood that the invention may be embodied in other specific formswithout departing from the essential characteristics thereof. Thepresent embodiments are therefore to be considered in all aspects asillustrative, and not restrictive. The scope of the invention isindicated by the appended claims rather than by the foregoingdescription.

What is claimed is:
 1. A photosemiconductor module for being opticallycoupled to an optical fiber, comprising:a holder assembly; aphotosemiconductor and a lens which are fixedly mounted in said holderassembly coaxially along an optical axis; an optical connector joinedcoaxially to said holder assembly by lap laser beam welding and adaptedto be connected to the optical fiber; and a sleeve partially fitted overa portion of said optical connector so as to protectively cover at leasta portion of said holder assembly and a portion of said opticalconnector.
 2. A photosemiconductor module as claimed in claim 1, whereinsaid sleeve includes a hollow portion and a flange portion at an end ofthe hollow portion, said flange portion being adapted to be coupled to aconnector assembly having an end of the optical fiber and beingdetachably connected to said optical connector.
 3. A photosemiconductormodule as claimed in claim 2, wherein said flange portion includes asubstantially oblong-shaped flange.
 4. A photosemiconductor module asclaimed in claim 2, wherein said flange portion includes a substantiallysquare-shaped flange.
 5. A photosemiconductor module as claimed in claim2, further comprising a filler filled between the hollow portion of saidsleeve and said holder assembly.
 6. A photosemiconductor module asclaimed in claim 1, wherein said holder assembly comprises at least onehollow holder, in which said lens is coaxially fixedly mounted, saidhollow holder being made of a material, including stainless steel, whichcan be joined to said optical connector by lap laser beam welding.
 7. Aphotosemiconductor module for being optically coupled to an opticalfiber, comprising:a hollow holder in which a photosemiconductor and aglass lens are fixedly coaxially mounted; a coupling in which an endportion of said hollow holder is fitted, said coupling having a flangeportion at an end thereof; said glass lens being disposed between saidphotosemiconductor and said flange portion of said coupling and beingfixedly mounted in said hollow holder by soldering; an optical connectoradapted to be optically coupled to said optical fiber; and said flangeportion of said coupling being joined to said optical connector by laserbeam welding.
 8. A photosemiconductor module as claimed in claim 7,wherein said coupling is made of a material, including stainless steel,which can be joined to said optical connector by lap laser beam welding.